Couplings for connecting hoses and other conduits which carry fluids have been in use for many years. One common form of such couplings, often referred to as cam and groove couplings or cam-lock couplings or cam locking quick-disconnect couplings, includes a female coupling unit on which a pair of cam arms are pivotally mounted in openings extending through the wall of the female coupling unit to the bore of the female coupling member and a male coupling unit, having a groove in an outside surface, is received in the bore of female coupling unit and is engaged by the cam arms in the groove of the male coupling unit to fix the male coupling unit in the female coupling unit. In an initial position in which the male coupling unit is inserted into the bore of the female coupling unit, the cam arms are pivoted radially outward providing clearance for the male coupling unit to be inserted. After the male coupling unit is inserted into the bore of the female coupling unit, the cam arms are pivoted inward drawing the male coupling unit into the bore of the female coupling unit to fix the male coupling unit in place while compressing a compressible sealing ring carried in a groove in the bore in the female coupling unit. To disconnect the coupling, the cam arms on the female coupling unit are pivoted outwardly to free the male coupling unit and permit removal of the male coupling unit.
Pressure fluctuations in the system or physically dragging the coupling can cause accidental disconnection of the coupling and a potentially hazardous spill or pressure release. Because of such potential safety hazards, many efforts have been made to improve the locking together of the male coupling unit and the female coupling unit. In some, a safety lock has been added which holds the cam arms on the female coupling unit in a closed position which is effective against pulsating pressure but ineffective against opening when the coupling is physically dragged.
Padlocks have been added to the couplings to protect against both unintentional and unauthorized disconnection of the coupling. Typically, the arrangements which have included a padlock have not been sufficiently effective in providing the desired protection.
Other efforts in the design of such couplings have involved the inclusion of parts which can be easily lost or misplaced or the addition of parts which adds cost and complexity to the couplings. Certain designs of such couplings are prone to the collection of dirt or debris making the couplings ineffective or inoperative.
Yet another problem with a number of prior art couplings is that the pull rings, which are carried by the cam arms, can become lodged between the cam arms and the body of the female coupling unit resulting in improper closure and connection of the male and female coupling units. In addition, these pulls rings, which typically are carried loosely by the cam arms, are susceptible to being "hung up" on something as the coupling is physically dragged.